16 Mr. Seaward's Description of a Hydro-pneumatic Pump. 

 parts; of which makeGB = 16; FG = 8; EF=4; DE=2; 



ACD E F G B 



CD=1 ; and AC = 1. Then if we consider this whole line 

 equal to the space which the plunger moves over in one stroke 

 of the pump, it is plain that at B, the commencement of the 

 stroke, the force will be equal to one atmosphere only, repre- 

 sented by the vertical line Bb: but when the plunger has 

 reached G, it will have made half a stroke, and the force will 

 then be equal to 2 atmospheres, as shown by the line Gg= 

 2 xBb. Again, when the plunger is at F, it will have made 

 three quarters of the stroke, and the force will then be equal 

 to 4 atmospheres = F_/=4B&; and so on, until the plunger 

 arrives at C, when it will have made f i part of the stroke, 

 and the compression and force will then be equal to 32 atmo- 

 spheres equal the line Cc = 32 x Bb. 



Therefore if we consider bg, gf, fe, &c. as so many straight 

 lines, then will the areas Gb, Eg, Ef, De, &c. be nearly as 

 the momenta of the plunger passing over the several spaces 

 BG, GF, FE, &c. But these several areas Gb, F g, Ef, 

 &c. are all equal to each other ; therefore the whole of the 

 momenta of the plunger passing through the space BC, 

 will be equal five times the area GgbB; that is, equal to 5 x 



I2±^R = 5 xU x 16 = 120 . 



2 J 



To this must now be added the momenta of the plunger 

 passing from C to A, the last ^d part of the stroke, which 

 will be as 32 X 1 = 32* ; which added to the above gives 152. 

 We have now to deduct the pressure of one atmosphere which 

 has assisted the plunger in passing over the space BA ; that 

 is. 32 x 1 = 32, which taken from the foregoing quantity will 

 leave 120 for the whole absolute momenta of the plunger. Now 

 divide this quantity by the number of parts in the line AB 



* Because when the gas in the chamber is compressed equal to 32 at- 

 mospheres, it will then raise the valve and make its escape into the re- 

 ceiver, as we suppose the pressure not to exceed 32 atmospheres. 



( = 32), 



